Intel Core i7-4940MX vs Intel Xeon E3-1558L v5 Comparison

# Intel Core i7-4940MX vs Intel Xeon E3-1558L v5

The benchmark data shows a clear overall winner: the Intel Xeon E3-1558L v5 takes all six head-to-head wins, with deltas ranging from -11.4% to -12.0% across Cinebench R15, R20, and R23 in both single-core and multi-core tests. Despite this, both processors sit at the 43rd percentile among all CPUs, and their average benchmark scores are nearly identical: 1886 for the i7-4940MX versus 1882 for the Xeon E3-1558L v5, a difference of just 0.2%. The Xeon's newer Skylake architecture and higher memory bandwidth (34.1 GB/s versus 25.6 GB/s) contribute to its consistent lead, but the i7-4940MX remains competitive in its own right. The Xeon E3-1558L v5 is the better choice for anyone running multi-threaded workloads or requiring ECC memory support, while the i7-4940MX, with its unlocked multiplier, offers overclocking flexibility that the locked Xeon cannot match.

The Verdict

From the data, the Intel Xeon E3-1558L v5 is the superior performer in every measured benchmark category. It wins all six head-to-head tests, with the smallest margin being 11.4% in Cinebench R20 single-core and R23 single-core, and the largest being 12.0% in Cinebench R15 single-core. The Xeon also delivers a lower TDP of 45 watts compared to the i7-4940MX's 57 watts, meaning it achieves higher scores while drawing less power. For users prioritizing raw performance and energy efficiency, the Xeon is the clear pick. The i7-4940MX, however, has one significant advantage: its multiplier is unlocked, allowing manual overclocking beyond its 4.00 GHz boost clock. The Xeon's multiplier is locked, so its 3.30 GHz boost clock is the ceiling. If overclocking is a priority, the i7-4940MX becomes attractive despite its benchmark deficit. Additionally, the i7-4940MX uses the Intel Socket G3, which may be more accessible to enthusiasts, whereas the Xeon uses the soldered Intel BGA 1440 package, limiting its upgradeability in most systems. In summary, the Xeon E3-1558L v5 wins on outright performance and efficiency; the i7-4940MX wins on overclocking headroom and socket flexibility.

Architecture Differences

The two processors come from different architectural generations and process nodes. The i7-4940MX is built on the Haswell architecture using a 22 nm process, while the Xeon E3-1558L v5 uses the Skylake architecture on a 14 nm process. The process shrink from 22 nm to 14 nm is reflected in the transistor counts: the i7-4940MX has 1,400 million transistors on a 177 mm² die, while the Xeon packs 2,300 million transistors onto a slightly smaller 171 mm² die. This higher transistor density in the Skylake part contributes to its superior benchmark scores despite a lower base clock of 1.90 GHz versus the i7-4940MX's 3.10 GHz. Both chips feature 4 cores and 8 threads, with identical cache hierarchies: 64 KB L1 per core, 256 KB L2 per core, and 8 MB shared L3. Memory support differs significantly: the i7-4940MX supports only DDR3 in dual-channel configuration, while the Xeon supports both DDR3 and DDR4, also dual-channel, with a higher memory bandwidth of 34.1 GB/s compared to 25.6 GB/s. ECC memory is supported only on the Xeon, marking a key differentiator for workstation reliability. Integrated graphics also differ: the i7-4940MX has Intel HD 4600, while the Xeon features Iris Pro Graphics P555, which is positioned as more capable for graphics workloads. Both use PCIe Gen 3 with 16 lanes from the CPU. The Xeon targets the server/workstation segment, while the i7-4940MX is a mobile extreme edition part. Release dates differ by over two years: the i7-4940MX launched in January 2014, and the Xeon in May 2016.

FAQ

Q: Which processor has the higher boost clock?

A: The Intel Core i7-4940MX has a boost clock of 4.00 GHz, while the Intel Xeon E3-1558L v5 boosts to 3.30 GHz.

Q: Does the Xeon E3-1558L v5 support ECC memory?

A: Yes, the Xeon E3-1558L v5 supports ECC memory, while the i7-4940MX does not.

Q: Which processor is more energy-efficient based on the data?

A: The Xeon E3-1558L v5 has a TDP of 45 watts, which is lower than the i7-4940MX's 57 watts, and it still achieves higher benchmark scores.

Q: Can the i7-4940MX be overclocked?

A: Yes, the i7-4940MX has an unlocked multiplier, whereas the Xeon E3-1558L v5 has a locked multiplier.

Q: How do their average benchmark scores compare?

A: The i7-4940MX has an average benchmark score of 1886, and the Xeon E3-1558L v5 has 1882, a difference of only 0.2%.

Q: Which processor supports DDR4 memory?

A: The Xeon E3-1558L v5 supports both DDR3 and DDR4, while the i7-4940MX supports only DDR3.

Specification Differences

The two processors differ in several key specifications. The i7-4940MX has a base clock of 3.10 GHz and a boost clock of 4.00 GHz, while the Xeon E3-1558L v5 has a base clock of 1.90 GHz and a boost clock of 3.30 GHz. TDP differs: 57 watts for the i7-4940MX versus 45 watts for the Xeon. The socket types are different: Intel Socket G3 for the i7-4940MX, and Intel BGA 1440 for the Xeon. The architectures are Haswell (22 nm) for the i7-4940MX and Skylake (14 nm) for the Xeon. Transistor counts are 1,400 million versus 2,300 million, and die sizes are 177 mm² versus 171 mm². Memory support differs: DDR3 only for the i7-4940MX, DDR3 and DDR4 for the Xeon. Memory bandwidth is 25.6 GB/s for the i7-4940MX and 34.1 GB/s for the Xeon. ECC memory support is absent on the i7-4940MX and present on the Xeon. Integrated graphics differ: Intel HD 4600 versus Iris Pro Graphics P555. The market segments are Mobile for the i7-4940MX and Server/Workstation for the Xeon. The multiplier is unlocked on the i7-4940MX and locked on the Xeon. Launch MSRP is $1096 for the i7-4940MX and $396 for the Xeon. Release dates are 2014-01-19 for the i7-4940MX and 2016-05-30 for the Xeon. Part numbers are SR1PP for the i7-4940MX and SR2TU for the Xeon.

Head-to-Head Benchmarks

The Xeon E3-1558L v5 wins all six head-to-head benchmark comparisons. In Cinebench R15 multi-core, the Xeon scores 655 against the i7-4940MX's 580, a delta of -11.5%. The single-core R15 test shows a similar gap: 92 versus 81, a delta of -12.0%. Moving to Cinebench R20, the Xeon leads in multi-core with 2733 against 2418 (-11.5%) and in single-core with 385 against 341 (-11.4%). In Cinebench R23, the Xeon again wins multi-core with 6508 versus 5759 (-11.5%) and single-core with 918 versus 813 (-11.4%). The consistency of these margins is striking: every test falls between -11.4% and -12.0%, suggesting a uniform architectural advantage rather than a workload-specific one. The i7-4940MX also has Geekbench scores not listed for the Xeon: 3869 multi-core and 1227 single-core, but since the Xeon does not have Geekbench entries in the data, no direct comparison can be made there. The Xeon's wins align with its higher memory bandwidth (34.1 GB/s) and newer 14 nm process, which likely enable better instruction-per-clock efficiency. The i7-4940MX's higher clocks (3.10/4.00 GHz versus 1.90/3.30 GHz) are insufficient to close the gap, indicating that the Xeon's architectural gains outweigh the clock disadvantage.

Where Each One Wins

The Xeon E3-1558L v5 wins in every benchmark category present in the data, making it the superior choice for compute-heavy tasks such as video rendering, software compilation, and scientific simulations. Its multi-core wins in Cinebench R15 (655 versus 580), R20 (2733 versus 2418), and R23 (6508 versus 5759) demonstrate a consistent edge in threaded workloads. The single-core wins (92 versus 81 in R15, 385 versus 341 in R20, 918 versus 813 in R23) also make it the better option for lightly-threaded applications like legacy software or certain games. Additionally, the Xeon supports ECC memory and dual-channel DDR4, making it more suitable for server and workstation environments where data integrity is critical. Its lower TDP of 45 watts also positions it as a better choice for compact or thermally constrained systems. The i7-4940MX, despite losing all benchmarks, retains specific advantages. Its unlocked multiplier allows overclocking, potentially narrowing or reversing the performance gap in the hands of an enthusiast. Its socket type, Intel Socket G3, offers more flexibility for system builders who prefer socketed CPUs over soldered BGA packages. The i7-4940MX also has a higher base clock (3.10 GHz) and boost clock (4.00 GHz), which could provide snappier responsiveness in short, bursty tasks if the Xeon's low 1.90 GHz base clock causes noticeable latency. Finally, the i7-4940MX is categorized as a Mobile extreme part, which may appeal to users building high-end laptops, whereas the Xeon's server/workstation segment targets a different use case. Overall, the Xeon is the performance pick, while the i7-4940MX is the overclocker's pick.